Spectrophotometric curve reading apparatus



May, 3 1949 n G. B. REIMANN 2,469,129

SPECTROPHOTOMETRIC CURVE READING APPARATUS 74 46 76 y Y /NvE/vron GENE WE1/.5 BECKER RE/MANM F' IG 7 f r ,Arron/ver May 3, 1949. G. B. REIMANN 2,469,129

SPECTROPHOTOMETRIC CURVE READING APPARATUS l Filed Nov. 5, 1945 2 sheets-sheet 2 llllllllllllll A T TORNE Y Patented May 3, 1949 UNITED STATES PATET OFFICE SPECTRGPHOTMETRIC CURVE READING APPARATUS 6 Claims.

This invention relates to graph-interpreting instruments and more particularly to those adaptable for the mechanical evaluation of curves of a spectrophotometric nature, such as those derived from a conventional recording spectrophotometer.

An object of this invention is to provide a new and improved method of reading spectrophotometric curves that will avoid one or more of the disadvantages and limitations of the prior art.

Another object of the present invention is to provide a new and improved method of reading spectrophotometric curves that will facilitate the determining of the mathematical relation of the curves through the use of a mechanical device.

A further object of the invention is to provide a new and improved mechanism that can be employed to mechanically lay out curves or points on a graph sheet.

An additional object of this invention is to provide a new and improved method of reading spectrophotometric curves that will enable wavelength corrections to be applied to same, in a manner that permit an accurate and practical determination to be made.

Still another object of the present invention is to provide a new and improved mechanism for reading spectrophotometric curves that will facilitate the evaluation of readings; that will be convenient to use; that can be constructed in' portable form and will have other valuable features of scientific and practical value.

An object of this invention is to provide a spectrophotometric curve reader that will eliminate the undue eyestrain resulting from the many transverse and vertical movements, required by the eyes, in the reading of spectrophotometric curves.

Another object of this invention is to decrease the amount of time required to read spectrophotometric curves, particularly when a wavelength correction is required.

An additional object of this invention is to construct into a convenient, portable instru-- Other objects Will become apparent as the in- I vention is more fully set forth.

A spectrophotometer of the conventional recording type, when properly calibrated and opy Wavelength scale.

`ment.

erated, yields a spectrophotometric curve, which is unique for the color of the sample measured.

This curve is the first step in the process of reducing a color to its fundamental terms or elements, so that it may be expressed and related to all other colors.

After obtaining the spectrophotometric curve which is registered on a sheet of conventional graph paper, the second step is to read the curve. There are two general methods of reading curves. These are known as: (l) the selected ordinate method and (2) the weighted ordinate method. The device to be hereinafter described is applicable to either or both. The selected ordinate method requires reading points at ninety designated wavelengths throughout the visible spectrum and a simple form of computation. The weighted ordinate method requires reading at but forty (40) designated wavelengths throughout the visible spectrum but this method together with a longer and more rigorous form of computation is generally used when careful standardization and precision in required, as, for example, in the standardization of railway signal glasses or in setting up speci- Iications for national and international color When the latter method is required standards. it is customary, when measuring such samples on the spectrophotometer, to measure at the same time and on the same graph sheet, certain standards which have been previously calibrated and Whose spectrophotometric values are known. These standar-ds serve as checks on the instrument and on errors of all kinds, such as the positioning of the graph paper in the instru- The positioning of the paper in the instrument aifects the positioning of the wavelength scale, which in turn can result in introducing errors of considerable magnitude into the measurement. The graph paper itself, due to shrinkage or expansion, caused by humidity changes, can cause the wavelength to shift from its true position by as much as Several millii microns. In careful standardization work, therefore, certain standards are used to correct the how much the wavelength scale should be adjusted (in either a plus or minus direction or both) to give a true reading for the measured sample or samples at the forty (40) wavelengths or points throughout the visible spectrum to be read. Any one graph sheet, in addition to the calibration curves, may have one or a dozen sample curves recorded on it, depending upon the nature of the sample (mixture of the dyes,

These corrections represent etc.) and the purpose of the work. Each graph sheet usually has a diierent Wavelength correction but the correction to be applied to each and all curves on any one graph sheet are the same. The instrument to `be described may be used for reading curves with or without the wavelength correction.

The determinationv of a reading for a. single point on. a spectrophotometric curve requires a concentrated visual inspection of that point Where the spectrophotometric curve and the. wavelength cross each other, and if a wavelength correction is required, the application ofA the Wavelength correction indicated for that point:

and finally, reading this adjusted or corrected point in terms of the reflectance scale, found at the left of the graph sheet.

The smallest subdivision on the conventional graph sheet from which spectrophotometric curves are read, may beV as minute as one (1) millimeter. Wheninaking a. reading and ap pl'ying a wavelength correction, this division is 'further subdivided intotwenty. (20) parts-l This. minute subdividing isv clone by visual estimate at eaeh o'f the forty (40) wavelengths of the visible spectrum. If a magnifyingv lens isr used in estimatingL the amount" off wavelength correction at -eachgiven. point, the-.wavelentgh scale as well as thereiiectance-scale 13o-which each .ofi these points must"V be referred is usually. out of*v thelineof sight and thereyesmust continuously reacooimmodate andi 11e-focus when makingl the 1 determinations.

In determining the-valuesfiorVr a single spectrophotometric curve, iequiringno wavelength correctio'n, the eye must travel'.I .in transverse and vertical. directions. at leastb one` hundred and twentyv (120.) times; in determining the values forv a single spectrophotometric curve requiring a wavelength correction.; the eye-must travel in. transverse and vertical directions, continuously. ire-accommodating.and re-focusing itself, at least one hundredand sixty times.

Conventional 'existing devices used for-deter'- miningl the values of spectrophotometric curves` cause. eye -strain. and discomfort' and at best-aretedious :to operate 'anditirr'ie consuming.

In lorderthat the inventionmaybe morerclearly understood attention.4 is hereby directed to the appended.- dra'win'gs, forlmin'g part of this' application and' illustrating one embodiment of tlie4 arrows6-6 of AFigure "l, showing the method 'of holding the wavelength scale;

`Figure '-7 is a Ase'ctfionalview taken through the wavelength Ascal'ean'd holding "device, and

Figure is a plan view 'o' thewavelength scale with -a typical Wavelength correction applied.

Similar reference characters "refer to similar parts throughout the 'drawings'.

The construction of'the instrument is divided into t'hlee inain parts: (l). a Atable on which y ygra'lcihs and 'curves are read', '(2) a stand `for supporting the table, and (3) the wavelength setting mechanism that is mounted on the table for alignment With the curves on the graphs and for reading these curves at any point in the visible spectrum. The stand consists of a base I I having a vertical post I2 formed into a hinge element I3 having a hole for the insertion of a tightening bolt. L4... This bolt, I 4 has abar. lipassing through nearone end for two purposes, oneA for tightening the bolt, the other for providing a handle for turning the whole instrument around on whatever surface it may be situated. A hinge element llcoacting Wtih thev element I3 has two legs I1 straddling the latter and adjustably positioned by theholt. I4. A space I9 between the legs affords sucient clearance and a resilient capacity for them to1springwhen the bolt is tightened. They aremounted on the plate I8. This plate is attached to and supportsthe table 20, which can be tilted to various angles on the hinge., Guide channels 2-IL are placed longitudinally on the upper surface of thet-able 20.

'Ihemechanism` consists'of a reciprocable car riage 26 having-anv upper plane surfaceionwhichv the graph sheet 4f3i`s` attached. It is heldin any part of its travel by the right' and left hand" Withthe movement! of the carriage under it*- The bridge 46`is stationary on thetable'and carries 1 the pinion 48. with its knob 49 tooperate'the gearl rack. Thisvpermit's. the adjustable carriage 26 to travel horizontally under it andi over the table. 20,1 The carriage travel'. is controlled by a pinion 48- acting on the. rack .gear 29 when manually operated by its knob 48.

At1 the. front, and rear. of. the carriage 26. isI provideda reiiectance .scalemechanism for carrying a reflectance. scalegl. reilectance scaleV is attached as outlinedkintheiollowing. description, and is. useiiliforv conveniently..v locating, thescale. at.

anypoint on. the graph `for V.the convenience of, reading the item-sand comparsonsfthereoi. .At the front. of the..carriage .26; issitted` an. end. plate 30.y havin-g slots). 3i for .theA .guidance of. ay re.- ectancescale holder lwhich isv` moved transf4 versely back. and. forthzby thehandle a lower lei/.er -nQntion 3ft-oi the-holder7 is. half-threaded.

and swung out of engagement withthescrew .38...

by a. handle 35 .whichfmoyes thef lever .34- onits pivot.36.. Thaler/ier portion 34- is tensioned bya sprl-ng-A i3'I. anchoredrto. pins.-38 .on the lever 34zat, one end and on the holdenatthe athen end. 4The. scalev :.holdfer., 3.2. travels; .across .they front. vpart of the` carriage:- w-hen menait-threaded. lower lever portion `.311! engages-,thefthreadsci the? screw 39:`

when ,rottatedby--knob 46 tornan; bef moved rapidlyby disengagi-ng the.thm-zadenl nutportion from cont-actr .with screw 3B; The scale; holder rigidly holds aomovable, reiectance lscale-4I atlf the iront anda .ai ohannelled clip: .-4 2f supports; :it i-ns .slidable relation to 4the near :side or thev carriage:26. Mounted Yat the-near .topyportioni of thesbridge 46 is a channel 50 whichenclosesaraekgear151;.. and. acts.. as a, .guidestsupport ion an.- adjustable magnifyinglensfhearinghlock 52,. The lensbean ing'block is fitted with a gear 53 which engages 'It i's; held above the rack-gear and is rotated manually by a knob 54A which moves the lens 58 and glass 66 back and forth. Projecting upward from the bearing block 52 is a hollow cylindrical support 55 into which is 'inserted a lens arm 56 keyseated at its lower end to allow the key in the hollow cylindrical support to keep the lens aligned with the bearing block 52. The lens arm is threaded at its lower end and made adjustable vertically in the hollow cylindrical support by a nut 51 to allow the lens 58 to be adjusted up and down to vary its magnifying focus. The upper end of the lens arm 56 is connected to the lens 58 by adjusting nuts 59 and 80. The rear of the bearing block 52 is tted with supports 6l and rod 52 which is threaded at G3 for the reception of arms 64 which are positioned on the rod by a lock nut 55. lower end of the arms are attached to a transparent glass 5G having a hairline 61 therein to assist in the correct wavelength setting and readi'ng of the aforesaid curves. The glass 3B is moved transversely across the carriage 2t in a gradual and minute manner by the operation of the pinion 53 on the rack 5i and permits settings of the hair line 51 to .05 of a millimicron on the wavelength scale. Attached to one end of the rod 52 is a lever 68 for raising and lowering the transparent glass 66 from the spectrophotometric graph sheet 43. The bridge 46 is provided with slots 69 which allow nger nuts 1li attached to grippers 44 and alignment grippers 45 to pass through when the carriage 25 is moved longitudinally up and down the table 2U. The grippers 44 and alignment grippers 45 are kept in alignment by pins El when the inger nuts are loosened to insert the graph sheet 43. The rear lower end of the bridge 46 (shown in Figure 6) is furnished with a slotted portion 1l that supports two stops 12 and spring clips 13 to hold the removable wavelength scale 14 in position. The wavelength scale (shown in Figure 8) has permanent wavelength graduations 15 and is provided with an unmarked section 13 located near the front edge which can be inscribed with a lead pencil or the like to show the wavelength correction 11 to be applied to a specific graph sheet. A stop 18 attached to table 2B is provided to contact the base H and protect the mechanism in the front end of the table and prevent it from striking the surface on which the base E I is mounted. The movement of the carriage 26 towards the operator is limited by a projection il@ contacting the clamp 23.

5 Although the description has been given using a wavelength correction and by the weighted ordinate system of reading curves, the instrument may be used with or without a wavelength correction and is applicable to either the selected or weighted ordinate methods of analysis.

The operation of the device is as follows: A spectrophotometric graph sheet, with a vertical reilectance scale 82, at its left, a horizontal wavelength scale 83 at its lower edge (both scales being permanently engraved on its face) is lettered by properly identifying the wavelength calibration curve B5 and the sample curve 81. The positioning of the wavelength calibration curve 85 on the graph sheet is then compared with the true, known values for this curve and the dierence between the two is inscribed on the detachable wavelength scale 14, provided for this purpose. These differences are known as the wavelength correcticn and are used to determine the true reading at each of the forty wavelengths for The the spectrophotometric' curve of the sample ori samples measured.

The graph sheet 43 is placed on the carriage 26 and held lightly in place by grippers 44 and alignment grippers 45 through the adjustment of nger nuts 10 so that the reectance scale 82 at the left of the graph sheet 43 coincides with the alignment grippers 45. Any wavelength, but preferably one near the center of the graph sheet 43 is covered by the hair-line 51 through the rotation of knob 54 and the carriage 26 is moved to bring the graph sheet 43 up and down under the hair-line 51 through the rotation of knob de to allow the full length of the selected wavelength to pass under said hair-line; the sheet is thus aligned in the instrument and the finger4 nuts 1t tightened. The detachable wavelength scale 14 is placed in position in the instrument and the machine is then ready for reading a curve. The movable reflectance scale 4| having graduations 88 which coincide with the vertical reiiectance scale 82 is moved to a convenient position, the hair-line 61 is placed at the starting point to the eXtreme left of the graph sheet on the spectrophotometric curve 81 to be read. The reading for that wavelength or point is found by noting the wavelength correction, 11, applying it with the wavelength setting mechanism and then reading the reectance at the point where the spectrophotometric curve and the corrected wavelength cross each other. The result is -re-A corded on a data sheet provided for the purpose. The lens for magnifying the images of the spectrophotcmetrlc curve, the reiiectance scale and the corrected Wavelength scale is positioned over the hair-line 51 and is focused by rotating the nut 51. The transparent glass 66 and hairline 61 are moved horizontally across the sheet 43 by rotating the knob 54; the transparent glass is raised and lowered from the face of the spectrophotometric graph sheet by lever 68 when it is necessary for it to pass over the movable reilectance scale 4i. The graph sheet 43 is moved up and down under the removable wavelength scale through the rotation of knob 49. The movable reflectance scale 4l can be quickly moved over the face of the graph sheet 43 by pressing the handles 33 and 35 together and releasing the threaded unit 34 from engagement with the screw 33, when the approximate position desired has been reached, the handles are released and the threaded unit 34 again engages the screw 39 and the finer adjustment is obtained by rotating the knob 40. The shoe 25 bears on the edge of the carriage 25 and acts as a brake when the table and carriage are tilted; it is removed from contact with the edge of the carriage when handle 2d is pulled out; this allows the carriage to be moved easily. rI'he curve is read at each of the 40 wavelengths of the visible spectrum. Only 36 of these are shown on the conventional graph sheet but in precise work the curve is frequently extrapolated at l and 9i to give a reading at wavelengths 380 and 390 (at the violet end of the spectrum) and at 16B and 110 (at the red end of the spectrum).

The use of a glass 66 is a matter of convenience in this form of the invention, a piece of any other transparent material that would be serviceable under the same conditions could be used in place of it if it was more desirable to do so.

While but one general form of the invention is shown in the drawings and described in the specications it is not desired to limit this applic ation to this particular form or in any other Way otherwise .than limited: by thelsccpefthereof, as it.'

is appreciated that other forms. could be. madethat would use the .sameprinciplesy and come within the scopev of the, appended'. claims,

-fHaVing thus described. the.. invention, what. is. claimed. is:

V1. An..apparatus ofthev .class described come prising in combination a reciprocating .carriage including .a plate arranged` to support and` hold. a spectrophotometricv curveasheetin readable position thereon'. and with. clamps mounted. on. its sides, a scale includingy markings Afor determining the; ordinate values of the `curve on said sheet mounted on said carriage. .and movable across same-to. align with various'points. on said curVe-,:

another scaleon the carriage. for determining the-values of abscissae of .said curve, a table for supporting said' carriagearranged to provide a pathgor .the latter to reciprocate cn, means for supporting the table; and" enabling same toi-be tilted .to various angles. .and retained in such positions, av bridgev attached .to said. table and permanently located in a predetermined position thereover, .a magnifying lens movable across the bridge Vand :alignable with; the points .on said curve for the examination and evaluation. thereof, and meansforadjusting the lensonsaid bridge.

An.. apparatus of .the class. described. comprising in. .combination a. reciprocating carriage including.. an plate; arranged to support and' hold a spectrophotometric curve .sheet in readable position 'thereon'. and. with.. clamps mounted on itsv sides, escale including markings -or determining the-ordinate values. of the curveon said sheet mounted onl said. .carriageand'` movable across sameto align with Various. points on saidV cur-ve, anotherscale on thecarriage for determining the values of: abscissaeroil said curve, .a table supporting said carriage. arrangedto; provide a path for thelatter to. reciprocate on; .means iorsupporting the tablet and enabling sameto be tilted to various angles and retained in such positions, a bridge attached. to said tabley and. permanently located ina. predetermined position thereover, a magnifying. .-lens. movable. across `the bridge and alignable with the-points on said curve for the examination and. .evaluation thereof, means for adjusting the lens. on .said bridge, and. a. transparent panemounted onA said' bridge. including. cross lines arranged for adjustable placement over the sheet forA facilitating theevaluation of the curve in conjunction with the. markings on.I said scales.

.3; A spectrophotometric. graph! analyser comprisingfincombination, a table, a: swivelling stand therefor, a carriage moveably mounted'. on thetable in predetermined directions; and" including aglat. plate adaptedv toqhold- .a4 graph sheet in readable position thereon, afreectance scale on the; carriage at one vside theizeoffor aligning the graph sheet therewitnand; determining the value of the graph., a Wavelength scale mounted on thebridgeiarranged at right angles tothe direc tion'. of the rei'iectance` scale, adapted to align with the graph to determine. the. values thereof, a-bridge rigidlyl positioned on .said table, a magnifying lens means movably attached to saidY bridge so. as to permit its movement thereon and across the graph. for theexaminati'on olil said@ curve and'gcomparison with said scales.

4l .A spectrophotometric graph analyser com-- prising in combination, a table, a swivelling standl therefon a. carriage. movable` mounted on the table .in predetermined directions, and including anat. plate-.adapted to holda graph sheet in readable vposition thereon, a. `reflectance scale valueof .theV graph, axwave lengthv scal'ei mounted on the bridge; arrangedv at' right angles to the` direction ofthe reectance scaleadaptedztofalign, With the graph toV determine .the valueszthereof; .as

bridge rigidly positioned onxzsaid tabla. a. mag-f.

nifying lens means; movably .attached to said. bridgeA so as to' permit its movement thereon and; across the graph for thefexamination; of'fsaid' curvevand. comparison with saidv scales, anda transparent pane with crosslinesnof predeter mined form thereon, mounted on said bridgeftor` cover- ,said sheet, said crosslines and markings on the scales being `.coordinated to permit the. spectrometric evaluation of any point onsaid?. graph.

.5. A spectrophotometricgraph analyser com prisingin combination, atable, a swivelling .standtherefor, a carriagey movably mounted on'the table in predetermined directionsandincludingf a; '.fiat .plate adapted to .hold a graph ,sheetin readable positionv thereon, a reflectance scale :on: the-carriage at one side thereof for aligningtthe` gra-phsheet therewith, and determining the Avaluey of the graph; a wave. length scale mountedonthe bridge arranged. at right. angleszto the direc-v tiong `of the reflectance scale, adapted to align. with the graph tosdetermine. the values..thereof,`

a bridge rigidly positioned onsaid table, aamagf.`

nifying lens means. movably` attached to said bridge so. as to .permit its movement. thereon@ and. across.v the graph for. the .examination of.. said curve .and comparison. with saidv scales, atrans-4 g, parent pane with crosslines of predetermined form Vthereon mounted. on. said .bridge to.` cover; said sheet, said crosslines and-markings on.the

v scales. being coordinated to' permit v:the spectrometric. evaluation. of any point .on said grapir. rack. and piniony means .for Vthe manual adjust-h ment of. the .carriageand lensover the. table and` graph thereon. Y

6L A spectrophotometric .graph analyser com-.- pris-ing in combination, a. table, including` a. swivelling stand therefor, .a carriage moi/'ably` mounted on the tablein predetermined directions. and including aat plate. adapted-tohclda graph-` sheet in. readable position thereon,..a. reflectance scale onthe carriage. at onesidethreof. for. align ingy the graph sheet therewith,-and determining; the value of the graph, a. wave length. scale. mounted on. the. bridge arranged at. right angles, to the direction of the reflectance scale, adapted. to align With the grap-nto. determine the Valuesv thereof, a bridge rigidly positioned onsaid,.taltile,

a. magnifying lens meansv movably attached to. said bridge so as to permity itsmovementthereon. and. across the graphf'or the. examination ofsaid. curve and comparison with said scalesL a trans.- parent pane with cro-ss lines.. of predetermined form thereon, mounted' on said bridge tocover said' sheet, said crosslines'. and: markings on., the scales being. coordinated, .to permit the, spectrometriic evaluation ofv any point on said graph,v

.. rackand pinion means for the. .manualad'justment oft they carriage and lens.over the table and graph thereon, said pane .including a hairline for aligning selected points on" said graph .and permitting saidf lens to' be` placed in more. coni spicuousalignment `under the lens, said table' (References on following page) mi REFERENCES CITED Number Name Date The following references are of record in the 115,15216 Cruger Jan' 25 1927 fue of this patent: 1,736,914 Huebner Nov. 26, 1929 1,977,213 Slobey Oct. 16, 1934 UNITED STATES PATENTS 5 1,993,589 Borden Mar. 5, 1935 Number Name Date 443,359 Duncan Dec. 23, 1890- FOREIGN PATENTS 1,245,311 Black Nov. 6, 191'7 Number Country Date 1,370,870 Zuraweck Mar. 8, 1921 2,330 Great Britain 1914 1,491,547 Rembielinski Apr. 22, 1924 10 

